According tot the report, on the evening of July 5, 2013, the Montreal Maine & Atlantic Railway train was parked on a descending grade in Nantes, Quebec. Officials said the engineer applied the hand brakes on all five locomotives, two other cars and shut down all locomotives except for the lead one.

The report said railway rules require hand brakes alone to be capable of holding a train, and this must be verified by a test.

However, the locomotive air brakes were left on during the test, meaning the train was being held by a combination of hand brakes and air brakes, giving a false impression that the hand brakes alone would hold the train, according to investigators.

Later in the night a fire started in the train's engine. Emergency responders put out the fire and shut off the engine, causing the air brakes to slowly fail.

Investigators said without enough force from the hand brakes, the train started rolling downhill toward Lac-Megantic, seven miles away.

According to the report, as the train moved downhill, it picked up speed, reaching 65 mph. The train derailed in downtown Lac-Megantic causing more than 1.5 million gallons of crude oil to spill, causing the massive explosion that killed 47 people.

The TSB said it found MMA had a weak safety culture, and learned that Transport Canada did not audit MMA thoroughly enough to ensure the company was operating safely.

The TSB said it also discovered that there were problems with training, employee monitoring and maintenance practices at MMA.

"Accidents never come down to a single individual, a single action or a single factor. You have to look at the whole context. In our investigation, we found 18 factors played a role in this accident," said TSB chair Wendy Tadros.

TSB officials also issued two new recommendations as part of the report that require Canadian railways to put in place additional physical defenses to prevent runaway equipment, and require the Canadian Department of Transport audit the safety management systems of railways in depth and more frequently.

MMA went bankrupt as a result of the disaster and was purchased earlier this year by an investment group.